Ischemic heart disease is the leading cause of deaths among patients in the world today. Discovering novel mechanisms during ischemia and developing efficacious and clinically relevant therapeutic strategies hold promise in the treatment of the ischemic heart. The latest emerging evidence suggests that among the leading mechanistic approaches in mediating myocardial ischemic injury is acetylation/deacetylation. Our recent focused works have demonstrated that inhibition of histone deacetylases (HDAC) leads to a profound cardioprotection, which is closely associated with p38 mitogen-activated protein kinase. p38 is one of the most important mechanisms in regulation of myocardial ischemic injury, development, and hypertrophic response. By using interdisciplinary approaches, our innovative discovery recently documented that p38 is subject to regulation by acetylation. We have identified that p38 is acetylated at lysines 15, 53, and 121 amino residues, respectively. The intriguing preliminary study and established works from our lab strongly support a functional role for p38 acetylation in protecting the heart against ischemic injury. However, the physiological function and molecular mechanism by which acetylation of p38 mediates cardiac injury and protection remain unknown. These exciting and novel findings lead to our current hypothesis that p38 acetylation is a signaling mechanism critical for myocardial protection and regulation of downstream substrate HDAC4 to form a partnership in the genesis of protective events. The specific aims of our proposed studies are the following: Specific Aim 1: Determine if p38 acetylation is essential for cardiomyocytes to survive against hypoxia in vitro. Specific Aim 2: Elucidate the physiological role of p38 acetylation in mediating myocardial injury and cardiac remodeling. Specific Aim 3: Investigate the role of p38 acetylation-mediated HDAC4 inactivation in the regulation of cardioprotection. Specific Aim 4: Use a preclinical large animal model to examine the role of p38 acetylation in HDAC inhibition-induced myocardial protection. Taken together, the proposed aims will for the first time establish that activation of p38 acetylation associated with HDAC4 inactivation prevents myocardial injury. All of these studies will not only uncover a novel and exciting mechanism in cell signaling and myocardial protection, but will also have great potential to develop a new therapeutic approach to improve human health.